During the past year, further investigations were conducted into the process of water movement and of energy transduction in the nervous system by measuring mechanical and thermal changes during excitation and inhibition. Continuous efforts were made to improve the sensitivity and the time-resolution of the detectors (devised and fabricated in this laboratory) employed in these inves- tigations. Attempts were also made at constructing new types of detectors for measuring rapid mechanical, thermal and optical changes in the nervous system. Significant achievements made during the past year include (1) elucidation of the process of nerve excitation and conduction in the garfish olfactory nerve by measuring both swelling and heat production during excitation, (2) analysis of the secretory process in the guinea pig pituitary gland by taking mechanical changes in the gland as an index, (3) studies of the mechanism of synaptic transmission in the cervical sympathetic ganglion of the guinea pig, and (4) demonstration of heat production of an unusually great magnitude evoked in the orthodromically activated olfactory bulb (bullfrog) in association with triphasic mechanical changes (swelling-shrinkage-swelling). All these studies are either already completed or near completion. It was repeatedly demonstrated in these studies that the method of recording non- electrical signs of nerve excitation and of synaptic transmission and inhibition reveals important properties of the nervous system which are inaccessible to conventional electrophysiological methods.